Derivatives of triazoly-imidazopyridine useful as ligands of the adenosine A2a receptor and their use as medicaments

ABSTRACT

Compounds of formula (I) 
     
       
         
         
             
             
         
       
         
         
           
             wherein: X is CH or CH—R 2 ; R 1  is C 1 -C 6  linear or branched alkyl or C 1 -C 6  linear or branched alkenyl; R 2  is hydrogen, C 1 -C 6  linear or branched alkyl or C 1 -C 6  linear or branched alkenyl, C 6 -C 14  aryl or C 6 -C 14  aryl(C 1 -C 6 ) linear or branched alkyl or C 6 -C 14  aryl(C 1 -C 6 ) linear or branched alkenyl, with the aryl group optionally substituted by one or more substituents, either the same or different, selected from the group consisting of halogen, hydroxy, C 1 -C 6  alkoxy linear or branched or C 1 -C 6  alkenyloxy linear or branched, amino, optionally mono- or disubstituted with C 1 -C 6  linear or branched alkyl; R 3  is NH 2 , or NHR 4 ; R 4  is C 1 -C 6  alkyl or C 1 -C 6  hydroxyalkyl, C 1 -C 3  alkoxyalkyl, amino(C 1 -C 6 )alkyl, where the amino group is optionally substituted with one or two C 1 -C 3  linear or branched alkyl groups, or with one or two C 2 -C 3  alkenyl groups C 6 -C 14  aryl or C 6 -C 14  aryl(C 1 -C 6 )alkyl, with the aryl group optionally substituted by one or more substituents, either the same or different, selected from the group consisting by halogen, hydroxy, C 1 -C 6  alkoxy linear or branched or C 1 -C 6  alkenyloxy linear or branched, amino, mono- or di-substituted with C 1 -C 6  alkyl linear or branched or C 1 -C 6  alkenyl linear or branched; and their pharmaceutically acceptable salts. These compounds are antagonists of the adenosine A 2a  receptor and useful as medicaments, in particular for the treatment of Parkinson&#39;s disease.

This application is a divisional of application Ser. No. 10/484,491filed Jan. 22, 2004, now U.S. Pat. No. 7,230,102 which in turn is the USnational phase of international application PCT/IT02/00489, filed inEnglish on 25 Jul. 2002, which designated the US. PCT/IT02/00489 claimspriority to IT Application No. RM01A000465 filed 31 Jul. 2001. Theentire contents of these applications are incorporated herein byreference.

The present invention relates to derivatives oftriazolyl-imidazopyridine and of the triazolylpurines, useful as ligandsof the adenosine A_(2a) receptor, to a process for their preparation, totheir uses as medicaments, in particular, for the treatment ofpathologies which benefit from the inhibition of this receptor, and tothe pharmaceutical compositions comprising them.

BACKGROUND OF THE INVENTION

Current therapy for Parkinson's disease is limited to the alleviation ofthe symptoms, but no agent has yet been identified capable ofcounteracting the establishment and the progress of the degeneration ofthe dopaminergic neurons of the substantia nigra linked with deficientdopamine levels of the basal ganglia in turn responsible for theappearance of the complex symptomatology of this pathology. This ischaracterised by rigidity, tremors, bradykinesia, akinesia, posturechanges; manifestations that represent a serious threat to the health ofthe individual with Parkinson's disease.

Among the therapeutic strategies currently used to improve the qualityof life of these subjects, are therapeutic approaches which aim toreplenish the missing neurotransmitter. One example is represented bythe use of L-DOPA, in combination with carbidopa or benserazide(inhibitors of the peripheral amino acid decarboxylases enzymes). Thistherapy is one of the most effective and currently used against theappearance of changes in motor function which are manifested when thephysiology of the dopaminergic system is severely compromised.

However, in the long run, this therapeutic approach is subject to alowering of efficacy. Indeed, patients subjected to chronic treatmentwith L-DOPA frequently display an emphasising of said manifestations, inaddition to the appearance of other side effects, due to the inherentlyneurotoxic properties possessed by L-DOPA.

Alternatively, the use of dopaminergic receptor agonists has beenintroduced, however they do not display the same efficacy as L-DOPA; orof monoamine oxidase inhibitors and of the muscarinic acetyl cholinereceptor antagonists. The use of the latter brings about the appearanceof serious side effects and cognitive impairment, as a consequence ofthe receptor interactions these products establish, both at the systemiclevel and at the central nervous system level.

In recent years, with the discovery of the role of adenosine as aneurotransmitter, its receptors and their functional characterisation,the hypothesis of using antagonists of the adenosine A_(2a) receptor astherapeutic agents for the treatment of the motor disorders associatedwith Parkinson's disease has gained credit. (P. J. Richardson, H. Kaseand P. G. Jenner Trends Pharm. Sci 1997, 18:338-345).

Recent experimental evidence has allowed the understanding of thedistribution, the function and the physiology of this receptor at thelevel of the central nervous system, permitting the conclusion thatblocking the A_(2a) receptor can modulate cholinergic, gabaergic andglutamatergic neurotransmission, in order to establish, at the level ofthe basal ganglia output neurons, a neurochemical order which canadequately compensate acute or chronic Dopamine deficiency in thenigrostriatal system.

Furthermore, it has been observed that the A_(2a) receptor isfunctionally associated with that for Dopamine D₂ and that thestimulation of the former can reduce the binding capacity of the latterfor Dopamine. Thus it follows, that the blocking of the A_(2a) adenosinereceptor increases the interactive capacity of D₂ receptors towardsDopamine, favouring binding even in the presence of low levels of thisneurotransmitter in the synaptic space. (Ferre S., e al. (1991) Proc.Nat. Acc. Sci. U.S.A. 88, 7237-7241). For these reasons, selectiveantagonists of the A_(2a) receptor have been proposed as agents for thetreatment of motor disorders, with particular regard to Parkinson'sdisease.

In addition, it has been demonstrated that these agents offer an effectthat is synergic to the treatment with L-DOPA or with dopamine agonists,and can be used in conjunction with the Dopamine-substitutive therapies.In this case, the use of receptor A_(2a) selective antagonistsrepresents a further therapeutic advantage since, the dosages normallyrequired for L-DOPA therapeutic treatment could be reduced in quantity,or frequency of administration, thereby conserving the therapeuticefficacy.

The present invention relates. to compounds with affinity for theadenosine A_(2a) receptor, active as antagonists, useful in thepreparation of medicaments for the treatment of motor disorders inindividuals, which are associated with functional alterations in thebasal ganglia, forming part of the symptomatology of diseases such asParkinson's disease, Alzheimer's disease, Huntington's disease andWilson's disease; brought about by drugs (parkinsonism of classicneuroleptics) trauma, toxic agents (NOTP, manganese, carbon monoxide).

The present invention can also be used in the treatment of Parkinson'sdisease with “on-off” phenomena and Parkinson's disease withpreponderant dyskinesia.

In addition, having been demonstrated that, following ischaemic damageto the central nervous system, adenosine A_(2a) receptor antagonists caninhibit the toxic effects induced by the excitatory amino acids releasedin abundance after such phenomena, cerebral ischaemia and the mechanismsassociated with neurodegenerative processes represent other “targets”towards which A_(2a) receptor antagonists can display their therapeuticactions.

Selective antagonists of the adenosine A_(2a) receptor are described inCA 1.242.368, Boehringer Ingelheim, in the form ofimidazo-triazole-pyrimidine derivatives, in which their activity towardsthe A₁ receptor prevails towards the A₂ receptor; in WO 01/02409,Vernalis Res Ltd, derivatives of thieno- and furopyrimidine aredescribed as compounds useful in the treatment of motor disorders, forexample Parkinson; WO 00/24742, Fusijawa Pharm Co Ltd, describesderivatives of pyrazolopyridine with dual antagonistic action againstthe A₁ and A₂ receptors; WO 00/17201 and WO 98/42711, Kyowa Hakko K K K,describe derivatives of 1,2,4-triazolo-(1,5-c)pyrimidine; WO 00/13682,WO 00/13681 and WO 99/26627, Cerebrus Pharm Ltd, describe derivatives of4-quinolinemethanol; WO 99/62518, Cadus Pharm Corp, describe7-deazapurine N-6 substitutions with activity profiles as A₁, A₂,A_(2a), A_(2b), A₃ receptor antagonists; WO 99/43678, Kyowa Hakko K K K,describe derivatives of 1,2,4-triazolo-(1,5-a)-pyrimidine; WO 95/01356and WO 98/52568, Schering Plough SpA, describe1,2,4-triazolo-(1,5-c)-pyrimidine.

Amongst the A_(2a) receptor antagonists in advanced testing phase, wecan mention compounds KW-6002 and KW-1783, described in EP 0 628 311,which can be characterised as xanthine derivatives. These productspossess a (3,4-dimethoxyphenyl)ethylenic group in position 8, and aresubject to loss of activity through photoisomerisation of the ethylenicbond (Annals New York Academy of Sciences—Ongini E.; Adami M; Ferri C;and Bertorelli R.; Trends in Pharm. Sci. 1996 Vol. 17 364-72). Thecompound KW 6002 is currently undergoing clinical trials (phase II as anantidepressant and phase III as an antiparkinson agent; PharmaprojectsAcc. No. 23891). Another selective antagonist of the A_(2a) receptor isthe product SCH 63390 (Pharmaproject Acc. No29842), in pre-clinicaltrials. ZM 241385 from Astra Zeneca (EP 0 459 702) is a potent selectiveantagonist; for this reason, utilised for pharmacological investigations(Ji X. D., Jacobson K. A., Drug Des. Discov. 1999, 16:217-226;Pharmaproject Acc. No 22730). Despite its high selectivity and affinity,in vivo the product has shown very low bioavailability (El Yacoubi M; etal Eur. J. Pharm. 401 (2000) 63-77).

SUMMARY OF THE INVENTION

It has been found that compounds with the formula

where: X is N, CH, C—R₂;

R₁ is C₁-C₆ linear or branched, saturated or unsaturated alkyl;

R₂ is hydrogen, C₁-C₆ linear or branched saturated or unsaturated alkyl,C₆-C₁₄ aryl or C₆-C₁₄ aryl(C₁-C₆) linear or branched, saturated orunsaturated alkyl with the aryl group optionally substituted by one ormore substituents, the same or different, selected from the groupconsisting of halogen, hydroxy, C₁-C₆ linear or branched, saturated orunsaturated alkoxy, amino, mono- or di-C₁-C₆ linear or branched alkyl;

R₃ is NH₂, NHR₄

R₄ is C₁-C₆ alkyl or C₁-C₆ hydroxyalkyl, C₁-C₃ alkoxyalkyl,amino(C₁-C₆)alkyl, where the amino group is optionally substituted byone or two C₁-C₃ alkyl groups, said alkyl groups are either linear orbranched saturated or unsaturated, C₆-C₁₄ aryl or C₆-C₁₄aryl(C₁-C₆)alkyl, with the aryl group optionally modified by one or moresubstituents, the same or different, selected from the group constitutedby halogen, hydroxy, C₁-C₆ alkoxy linear or branched saturated orunsaturated, amino, mono- or di-substituted by C₁-C₆ alkyl linear orbranched saturated or unsaturated and pharmaceutically acceptable saltsthereof, possess affinity for the A_(2a) receptor.

Therefore, an object of the present invention are formula (I) compoundsdefined above and the pharmaceutically acceptable salts thereof.

Another object of the present invention are the processes for thepreparation of formula (I) compounds defined above, their use asmedicaments, in particular for the preparation of medicaments withinhibitory activity, also selectively, of the A_(2a) adenosine receptor,such medicaments being useful for the treatment of pathologiesresponsive to the inhibition of the adenosine A_(2a) receptor, such asthe treatment of motor disorders, Alzheimer's disease, Huntington'sdisease, Wilson's disease and Parkinson's disease. The compoundsaccording to the present invention are also useful for the preparationof medicaments for the treatment of cerebral ischaemia and/or themechanisms associated with neurodegenerative processes.

Further objects of the present invention are pharmaceutical compositionswhich contain at least one formula (I) compound as active ingredient.

This and other objects of the present invention will be illustrated ingreater detail also by figures and examples, where:

in FIG. 1 it is shown the evaluation of the capacity to induce catalepsyin mice;

in FIG. 2 it is shown the effect of exemplary compounds of the presentinvention on CGS 21680—induced catalepsy. Each column represents meanscore catalepsy±s.e. of 10 animals per group;

in FIG. 3 it is shown the effect of exemplary compounds of the presentinvention on Haloperidol induced catalepsy, in mice. Each columnrepresents the mean catalepsy score±s.e. of 10 animals per group;

in FIG. 4 it is shown the combination effects of exemplary compounds ofthe present invention with sub threshold dose of L-DOPA plus benserazide(12.5 mg/kg and 6.25 mg/kg, i.p., respectively) on Haloperidol-inducedcatalepsy in mice;

in FIG. 5 it is shown the effect of exemplary compounds of the presentinvention in mouse forced swim test. Mice were injected with vehicle orthe test compound or Imipramine 60 minutes before the test. The durationof immobility was recorded during 4 minutes of the testing period. Datarepresented are mean±s.e. of 10 mice per group. ANOVA and Tukey's test**=p<0.01 vs. controls.

DETAILED DESCRIPTION OF THE INVENTION

In the formula (I) compounds, examples of C₁-C₆ saturated or unsaturatedalkyls are methyl, ethyl, propyl, isopropyl, butyl, sec-butyl,ter-butyl, pentyl, hexyl, ethylene, propylene, butylene. The alkenylsand the alkinyls may contain up to the maximum possible degree ofunsaturation, and the alkyls, alkenyls and alkinyls may be representedby all the theoretically possible isomers. In the formula (I) compounds,examples of C₆-C₁₄ aryl or C₆-C₁₄ aryl(C₁-C₆)alkyl, with the optionallysubstituted aryl group are phenyl, naphthyl and anthryl, at various bondpositions (for example 1- or 2-naphthyl), benzyl, phenylethyl,phenylpropyl, phenylbutyl, phenylpentyl, phenylhexyl, arylalkylanalogues with naphthyl and anthryl, 2-, 3- or 4-phenyl groupssubstituted by the above mentioned groups, for example 2-, 3- or4-hydroxyphenyl, 2-, 3- or 4-alkoxyphenyl, where the alkyl residue is asdescribed above, 2-, 3- or 4-halophenyl, where the halogen is fluoro,chloro, bromo, iodo, 2-, 3- or 4-aminophenyl, where the amino group canbe mono or di substituted with an alkyl group as described above. Theperson skilled in the art will easily be able to characterise all thepossible compounds predicted for formula (I) defined above, making theappropriate substitutions with the definitions given for the variousgroups.

Pharmaceutically acceptable salts of formula (I) compounds are all thesewith organic or inorganic acids capable of salifying the basic centrespresent, and which do not possess any toxic or otherwise undesiredeffects.

Amongst the formula (I) compounds, a first preferred group comprisesthose wherein X is nitrogen and R₂ is a butyl group in position 2.

A second preferred group is comprised of those wherein X is nitrogen andR₂ is a phenethyl group in position 2.

A third preferred group is comprised of those wherein X is nitrogen andR₂ is a pentyl group in position 2.

A fourth preferred group is comprised of those wherein X is carbon andR₂ is hydrogen in position 6 or 7.

The following compounds are particularly preferred:

-   6-amino-2,9-dimethyl-8-(triazol-2-yl)-9(H)-purine (ST 1491);-   2-butyl-9-methyl-8-(2H-1,2,3-triazol-2-yl)-9H-purine-6-ylamine-(ST    1535);-   9-methyl-2-(2-phenylethyl)-8-(2H-1,2,3-triazol-2-yl)-9H-purine-6-ylamine    (ST 1537);-   9-methyl-2-pentyl-8-(2H-1,2,3-triazol-2-yl)-9H-purine-6-ylamine (ST    2097).

As a particular case of the present invention, the compound6-amino-9-methyl-8-(triazol-2-yl)-9(H)-purine (ST 1490) revealedaffinity toward the A₁ adenosine receptor, therefore is useful for thepreparation of a medicament for the treatment of cognitive deficits,Alzheimer's disease, cerebral ischemia, acute and chronic renal failure,renal failure induced by radiografic contrast media or by cisplatin.

Formula (I) compounds can be prepared following the synthetic approachdescribed in the following diagram.

Compound a), obtainable through methods known in the literature, issubjected to be bromo-substituted at position 2, then the bromo issubstituted by the triazol-2-yl group.

The following diagrams 1A, 1Abis and 2A show, by way of example only,the processes for the preparation of the compounds briefly denominatedST 1491, ST 1536, ST 1535, ST 1537, ST 2097 and ST 1680.

The compounds indicated by the numbers (2) to (7) (diagrams 1A and1Abis) are obtained by synthetic procedures known in the literature,compound (1) is commercially available; compounds (8), (9) and (10), aredescribed in Heterocycles 1999, 721-726; J. Med. Chem. 32, 11, 1989,2474-2485; J. Heter. Chem. 23, 3, 1986, 669-672; J. Chem. Soc. 1955,2755-2758; J. Med. Chem. 39, 2, 1996, 487-493, J. Heter. Chem. 27, 3,1990, 563-566; (11) and (12) are described in EP 0 082 369 but thepresent invention provides a new preparation. The molecules from (13) to(14) are new, therefore they are specifically claimed as intermediatesof the process described in the present invention. Persons skilled inthe art, resorting to their general knowledge and to the literature, areable to prepare the other formula (I) compounds, different from theseexemplified in the preceding diagrams.

The following examples further illustrate the invention.

EXAMPLE 1

(Scheme 1A)

2-chloro-6-dibenzylamino-9(H) purine (2)

To a solution of 1 g of 2,6-dichloropurine (1) (97%, 5.13 mmol), in 30ml of absolute ethanol were added di-isopropylethylamine (1 ml, 5.13mmol) and distilled dibenzylamine (1.1 ml, 5.13 mmol). The reactionmixture was left to reflux for 20 hours (after 1 hour a whiteprecipitate is formed). The solvent was then removed at low pressure andthe residue taken up in water.

Following cooling and filtration the solid residue (2), was dried undervacuum.

Yield: 95%

R_(f)=0.25 (cyclohexane/ethyl acetate) 7:3

M.p.: 250-252° C.

¹H-NMR (200 MHz, CDCl₃): δ 7.89 (s,1H), 7.32 (s, 10H), 5.55 (bs, 2H),

5.49 (bs, 2H).

MS (m/z): 91; 258-260 (BP, M-benzyl), 349-351 (<5%,M).

2-chloro-6-dibenzylamino-9-methyl-purine (3)

To a solution of (2) in hot DMF was added 828 mg of K₂CO₃ (6 mmol). Thesolution was then cooled and treated with 0.46 ml of CH₃I (7.2 mmol)with agitation for about 12 hours. The DMF was evaporated, the producttaken up in water and filtered, and the residue obtained crystallised inethanol giving 1.45 g of product (3)

Yield: 78%.

R_(f)=0.38 (cyclohexane/ethyl acetate) 7:3.

M.p.: 144-146° C.

¹H-NMR (200 MHz, CDCl₃): δ 7.67 (s, 1H, H8-purine); 7.31 (s, 10H,aromatic); 5.5 (br, 2H, CH₂-benzylate); 4.93 (br, 2H, CH₂-benzylate);3.81 (s, 3H, CH₃).

MS (m/z): 91 (BP, benzyl); 272-274 (65%-20%, M-benzyl), 363-365 (<5%,M).

2-alkyl-6-dibenzylamino-9-methyl-9(H)-purine (4), (4c), (4e), (5)

(General procedure) In a nitrogen-filled flask were placed 700 mg of2-chloro-6-dibenzylamino-9-methyl-9(H)-purine (3) (1.93 mmol), 4 ml ofNMP (N-methylpyrrolidone), 3.8 mmol of alkyl tributyl tin and 140 mg ofPd(PPh₃)₄. These were stirred at 120° C., for 8 hours for compounds 4,4c and 4e and two hours for compound 5. These were cooled and dilutedwith-water (560 ml) and methylene chloride (50 ml) and the aqueous phasefinally extracted with methylene chloride (4×50 ml). The combinedorganic phases were washed in salt water, dried over anhydrous sodiumsulphate and the solvent evaporated thus obtaining a dark liquid. Theproducts were purified on a silica-gel column, (eluent:EtOAc/Cyclohexane 1/1) giving (4), (4c), (4e) and (5) in the form ofsolids or yellow oils.

(4): Yield:63%.

M.p.: 143° C.

MS (m/z): 278 (100%, M-benzyl); 91 (55%,benzyl).

(4c): Yield:90%.

M.p.: non-determinable—rubber-like substance.

MS (m/z): 294 (100%, M-benzyl); 91 (65%, benzyl). ¹H-NMR: 200 MHz,CDCl₃; δ 7.65 (1H, s, purine); 7.30 (10H, m, aromatics); 5.27 (4H, br,—CH₂-benzylate); 3.82 (3H, s, N—CH₃); 2.88 (2H, t, —CH₂—CH₂—CH₂—CH₃);1.80 (2H, m, —CH₂—CH₂—CH₂—CH₃); 1.37 (2H, t, —CH₂—CH₂—CH₂—CH₃); 0.91(3H, t, —CH₂—CH₂—CH₂—CH₃).

(4e) Yield: 65%.

6-dibenzylamino-9-methyl-2-pentyl-9(H)-purine

M.p.: non-determinable, rubber-like substance.

MS: m/z=399, 308, 220

¹H-NMR (200 MHz, CDCl3) δ (ppm): 7.71 (s, 1H), 7.30 (m, 10H), 5.30 (bs,4H), 3.80 (s, 3H), 3.38 (t, 2H), 2.38 (m, 2H), 2.02 (m, 2H), 1.30 (m,2H), 0.88 (m, 3H)

(5): Yield: 84%.

M.p.: non-determinable—rubber like substance.

MS (m/z): 340 (100%, M-benzyl); 91 (70%,benzyl).

6-dibenzylamino-2,9-dimethyl-9(H)-purine (4a)

In a refrigerated, three-necked, round-bottomed flask, under an inertatmosphere (nitrogen), were placed 1.07 g of (3) (2.94 mmol) dissolvedin 30 ml of anhydrous THF, 6 ml of trimethylaluminium 2M in toluene (12mmol), 27 mg of PdCl₂ (0.15 mmol) and 79 mg of PPh₃ (0.3 mmol). Thesewere reacted by refluxing for 48 hours. Terminating the reaction, themixture was poured into a beaker, chilled in an ice bath and the excesstrialkylaluminium destroyed by small additions of water and alcohol. Thealuminium hydroxide precipitate was filtered through paper, and themixture extracted with dichloromethane. Following evaporation of theorganic phase at reduced pressure the residue was purified by flashchromatography (SiO₂, cyclohexane/EtOAc 1:1). 900 mg of (4a) (2.62 mmol)in crystalline form were obtained.

Yield 89%.

M.p.: 117-118° C.

MS (m/z): 91 (80%, benzyl), 252 (BP M-benzyl), 343 (<5%, M). ¹H-NMR: 200MHz, CDCl₃ δ 7.65 (s, 1H, H8-purine); 7.30 (s, 10H, aromatics); 5.30(br, 4H, CH₂-benzylate); 3.81 (s, 3H, N—CH₃); 2.62 (s, 3H, C—CH₃).

2-isopropyl-6-dibenzylamino-9-methyl-9(H)-purine (4b) and2-(2-phenylethyl)-6-dibenzylamino-9-methyl-9(H)-purine (4d)

100 mg of (4) or (5) were placed in an autoclave with 5 ml of ethanol,heated until completely dissolved and then 50 mg of palladium ongraphite support added. This was left stirring overnight under 4atmospheres of hydrogen. The catalyst was filtered through celite andthe solvent evaporated under reduced pressure, giving (4b) or (4d) aswhite solids.

(4b): Quantitative yield.

M.p.: 82° C.

MS m/z: 280 (100%, M-benzyl); 91 (50%,benzyl).

(4d): Quantitative yield.

M.p.: 144° C.

MS m/z: 342 (100%, M-benzyl); 91 (100%,benzyl).

(Scheme 1A bis)

(5a,b,c,d,e)

General Procedure

In a reaction flask were solubilised 1.6 mmol of (4a), (4b), (4c), (4d)and (4e) in a mixture of 7 ml of MeOH, 7 ml of THF and 7 ml of acetatebuffer pH=4 (obtained by dissolving 4 g of sodium acetate in 100 ml ofwater and bringing to pH 4 with glacial acetic acid). 0.7 ml of bromine(13.6 mmol) were added very slowly dropwise and the mixture left at roomtemperature under stirring until the starting products had disappeared(about 12 hours). Excess bromine was decoloured with sodiummetabisulphite and the reaction alkalinised to pH=8 with a saturatedsolution of Na₂CO₃. After extraction with dichloromethane andevaporation of the solvent at reduced pressure, 1.2 g of yellow oil wereobtained for (5a), (5b), (5c), (5d) (5e), later purified on preparativechromatographic column.

(5a): Quantitative yield.

MS m/z: 91 (100%,benzyl); 330-332 (doublet, 70%, M-benzyl).

(5b): Quantitative yield.

MS (m/z): 91 (100%,benzyl); 358-360 (doublet, 70%, M-benzyl).

(5c): Quantitative yield.

MS m/z: 91 (100%,benzyl); 372-374 (doublet, 70%, M-benzyl).

(5d): Quantitative yield.

MS (m/z): 91 (100%,benzyl); 420-422 (doublet, 45%, M-benzyl).

(5e)

9-bromo-6-dibenzylamino-9-methyl-2-pentyl-9(H)-purine

M.p.: 97° C.

MS: m/z=479-477, 388-386

¹H-NMR (200 MHz, CDCl₃) δ (ppm): 7.28 (m, 10H), 5.16 (bs, 4H), 3.75 (s,3H), 2.79 (t, 2H), 1.79 (m, 2H), 1.29 (m, 4H), 0.86 (m, 3H)

2-Alkyl-6-dibenzylamino-9-methyl-8-(triazol-2-yl)-9(H)-purine(6a,b,c,d,e)

In a reaction flask, under an inert atmosphere, were placed 2 ml ofanhydrous DMF, 92 mg of NaH (80% in paraffin, 2.5 mmol) and slowly, 0.18ml of 1,2,3-triazole (2.5 mmol) were added and left under stirring forabout 1 hour. A solution of crude (5a), (5b), (5c), (5d) or (5e) (1.7mmol) in 5 ml of anhydrous DMF was added dropwise, slowly and left understirring at 100° C. for 12 hours. The DMF was evaporated and the residuepurified by flash chromatography (SiO₂, cyclohexane/EtOAc 7:3) giving(6a), (6b), (6c), (6d) or (6e) as white solids.

(6a): Yield: 20%.

M.p.: 161-163° C.

MS (m/z):91 (90%,benzyl), 319 (BP, M-benzyl); 410 (<5%, M).

¹H-NMR: 200 MHz, CDCl₃: δ 7.94 (s, 2H, H-triazole); 7.29 (s, 10Haromatics); 5.45 (br, 2H, CH₂-benzylate); 5.04 (br, 2H, CH₂-benzylate);3.96 (s, 3H, N—CH₃); 2.62 (s, 3H, C—CH₃).

(6b): Yield 20%.

M.p.: 140° C.

MS (m/z): 347 (100%, M-benzyl); 91 (75%, benzyl).

(6c): Yield 20%.

M.p.: 114° C.

MS (m/z): 361(100%, M-benzyl); 91(70%, benzyl).

¹H-NMR: 200 MHz, CDCl₃; δ 7.94 (2H, s, triazole); 7.30 (10H, m,aromatics); 5.49-5.21 (4H, d, br, —CH₂-benzylate); 4.12 (3H, s, N—CH₃);2.84 (2H, t, —CH₂—CH₂—CH₂—CH₃); 1.80 (2H, m, —CH₂—CH₂—CH₂—CH₃); 1.37(2H, m, —CH₂—CH₂—CH₂—CH₃); 0.92 (3H, t, —CH₂—CH₂—CH₂—CH₃).

(6d): Yield 20%.

M.p.: 173° C.

MS (m/z): 409 (65%, M-benzyl), 91 (100%,benzyl).

(6e)

6-dibenzylamino-9-methyl-2-pentyl-8-(triazol-2-yl)-9(H)-purine

M.p.: 139° C.

MS: m/z=466, 375, 348

¹H-NMR (200 MHz, CDCl₃) δ (ppm): 7.94 (s, 2H), 7.29 (m, 10H), 5.47 (bs,2H), 5.04 (br, 2H), 3.96 (s, 3H), 2.84 (t, 2H), 1.82 (m, 2H), 1.33 (m,4H), 0.88 (m, 3H)

2-Alkyl-6-amino-9-methyl-8-(triazol-2-yl)-9(H)-purine (7a,b,c,d,e)

In a refrigerated reaction flask under nitrogen, were dissolved 0.33mmol of (6a), (6b), (6c), (6d) or (6e) in 3 ml of anhydrousdichloromethane. 0.37 ml of CF₃SO₃H (3.3 mmol) were added slowly,dropwise, and the mixture left refluxing for six hours. The mixture wasthen loaded onto an activated alumina chromatographic column, firstlyeluted with 50 ml of dichloromethane to eliminate the strongly colouredaromatic derivatives, and then with CH₂Cl₂/ethanol 1:1 (40 ml), followedby ethanol (40 ml) and finally with saturated aqueous ammonia in ethanol(5%, 40 ml). The moieties containing the desired product were combinedand evaporated, giving a yellow solid which was purified by flashchromatography (SiO₂, AcOEt/EtOH 95:5), giving the pure products(7a,b,c,d,e) as white solids. Crystallisation in ethanol gave highlypure product in the form of small, very white crystals.

(7c) (ST 1535)

Yield: 55%.

M.p.: 182° C.

MS (m/z): 230 (100%, M-42); 243 (20%,M-29); 257 (10%, M-15); 272(<10%,M).

¹H-NMR: 200 MHz, CDCl₃; δ 8.00 (2H, s, triazole); 5.74 (2H, br, —NH₂);4.07 (3H, s, N—CH₃); 2.85 (2H, t, —CH₂—CH₂—CH₂—CH₃); 1.79 (covered bywater, m, —CH₂—CH₂—CH₂—CH₃); 1.43 (2H, m, —CH₂—CH₂—CH₂—CH₃); 0.97 (3H,t, —CH₂—CH₂—CH₂—CH₃).

(7b) (ST 1536)

Yield: 55%.

M.p.: 177° C.

¹H-NMR: (200 MHz, CDCl₃) δ 8.00 (2H, s, triazole); 5.70 (2H, br, —NH₂);4.07 (3H, s, N—CH₃); 3.10 (1H, sextuplet (J=6.82 Hz), CH₃—CH—CH₃); 1.36(6H, d (J=6.82Hz), CH₃—CH₂—CH₃).

MS: m/z: 230 (100%, M-28); 243 (95%,M-15); 216 (50%,M-44); 258(50%,M).

(7d) (ST 1537)

Yield: 55%.

M.p.: 164° C.

¹H-NMR (200 MHz, CDCl₃): δ 8.00 (2H, s, triazole); 7.3-7.18 (5H, m,arom.); 4.07 (2H, s, CH₂); 3.17 (2H, s, CH₂); 1.26 (3H, s, CH₃).

MS m/z: 91, 216, 243, 303, 320 (100%,M).

(7a) (ST 1491)

Yield: 43%.

M.p.: 238° C.

MS (m/z): 230 (BP, M).

¹H-NMR (200 MHz, CDCl₃): δ 8.00 (s, 2H triazole); 5.63 (br, 2H, NH₂);4.06 (3H, s, N—CH₃); 2.64 (3H, s, C—CH₃).

(7e) (ST 2097)

6-amino-9-methyl-2-pentyl-8-(triazol-2-yl)-9(H)-purine

M.p.: 154° C.

MS: m/z=286, 271, 257, 243, 230, 190

¹H-NMR (200 MHz, CDCl₃) δ (ppm): 8.00 (s, 2H), 7.26 (m, 10H), 5.56 (bs,2H), 4.06 (s, 3H), 2.83 (t, 2H), 1.84 (m, 2H), 1.40 (m, 4H), 0.91 (m,3H).

EXAMPLE 2

(Scheme 2)

4-hydroxy-3-nitropyridine (8)

16.7 ml of oleum (SO₃ 20% in H₂SO₄) was added slowly and dropwise to 20ml of fuming nitric acid chilled to 0° C., and over a period of 15minutes, 7 g of 4-hydroxypyridine were added. This was heated slowlyuntil nitration began (red vapours developed). The reaction was thencooled until said vapours disappeared, then refluxed for 1 hour.

The reaction mixture was slowly cooled to room temperature and thenpoured over 50 g of ice. 60 ml of concentrated aqueous ammonia (30%) wasadded in small doses, taking care the temperature did not rise above200° C. The pH was adjusted to 7.5 with more ammonia and then left at 4°C. overnight. The precipitate produced was filtered and crystallised inwater to obtain 7.1 g of (8) as clear yellow crystals.

Yield=70%.

M.p.: 275-277° C.

MS (m/z): 94, 140.

4-chloro-3-nitropyridine (9)

In a reaction flask under nitrogen, were reacted at 70° C., 51.5 g ofPCl₅ and 75 ml of POCl₃. At the same temperature was added carefully34.6 g of (8). The temperature was increased to 140° C. and the reactionrefluxed for 4 hours under nitrogen. To the cooled mixture, evaporatedunder vacuum, was added 100 ml of iced water. The pH was adjusted to 7.5by the addition of granular sodium carbonate, and 60 ml of methylenechloride added and the mixture stirred vigorously until all the residuehad completely dissolved. The phases were separated and the aqueous partwas extracted with more methylene chloride (5×30 ml). The combinedorganic phases were treated with anhydrous sodium sulphate andevaporated to obtain 29.9 g of (9) as a yellow, waxy solid.

Yield=76%.

MS (m/z): 85, 87, 100, 102, 112, 114, 158, 160 (M).

4-methylamino-3-nitropyridine (10)

29.9 g of (9) were solubilised in 200 ml of hot ethanol; to thesolution, brought to 0° C., were added slowly, dropwise, 103 ml of 35%aqueous methylamine. This was left stirring for 30 minutes and then theethanol evaporated. The residue was crystallised in water giving 24 g of(10) in the form of clear yellow crystals.

Yield=83%.

MS (m/z): 107, 120, 135, 153 (M).

2-chloro-4-methylamino-3-aminopyridine (11)

10 g of (10) were dissolved in 50 ml of 12N HCl and the temperaturebrought to 90° C. 72.5 g di SnCl₂.2H₂O were added in five portions overthe course of 1 minute. This was left stirring at 90° C. for 1 hour.After cooling the solution to room temperature, 100 ml of water wereadded and evaporated at reduced pressure. The residue was taken up in100 ml of water, cooled to 0° C. and concentrated aqueous ammonia added,until the formation of a white, gelatinous precipitate. The pH wasadjusted to 8.5-9 and the resulting emulsion centrifuged. The remainingsolid residues were again taken up in water and centrifuged. Theoperation was repeated three times. The combined solid residues wereleft under stirring overnight in 50 ml of methylene chloride. Thecentrifuged aqueous phases were extracted three times with methylenechloride, then all the organic phases combined, then dried overanhydrous sodium sulphate and subsequently evaporated under vacuum,giving 6.2 g of (11) in the form of pink crystals.

Yield=60%.

M.p.: 166-168° C.

MS (m/z): 76, 122, 142, 157(M+).

4-chloro-1-methyl-1(H)-imidazo[4,5-c]pyridine (12)

2,4 g of (11) were suspended in 97 ml of ethyl orthoformate, and DMFadded with agitation until the turbidity disappears. To the clearsolution obtained was then added 1.7 ml of 12N HCl. (after a few minutesof the addition of the acid, the solution becomes turbid) and left understirring, under nitrogen for 12 hours. The solvent was then evaporatedunder vacuum and the brown oily residue purified by flash chromatography(eluent: cyclohexane/ethyl acetate 20:80) giving 1.7 g of (17) as awhite solid.

M.p.: 137-38° C.

Yield=68%.

MS: m/z: 167-169 (100%-30%: M+); 132 (55%: M+-Cl); 105 (35%).

¹H-NMR (200 MHz, CDCl₃): δ 3.91 (s, 3H, N—CH₃); 7.33 (d, J=5.64 Hz, 1H,═N—CH═CH—), 7.98 (s, 1H, —N═CH—N(CH₃)—), 8.24 (d, J=5.64 Hz, 1H,═N—CH═CH—).

2-bromo-4-chloro-1-methyl-1(H)-imidazo[4,5-c]pyridine (13)

1.5 g (9 mmol) of (12) were solubilised, under nitrogen, in 25 ml ofanhydrous THF and the temperature of the mixture adjusted to −78° C. 8ml of BuLi 2.5 M (20 mmol) in hexane was added slowly. The solution tookon a reddish colour in testimony to the formation of an aromaticcarbanion in position 2. After 1 hour, 2 ml of bromine (40 mmol) werecarefully added dropwise, over a period of 30 minutes and then left withagitation for a further 2 hours. The temperature was brought slowly to0° C. and then a saturated solution of sodium metabisulphite addeddropwise until the bromine was completely destroyed. The pH of thesolution was adjusted to 9 with aqueous 2N sodium bicarbonate. Thesolution was extracted with methylene chloride. The combined organicphases were washed with salt water, dried over anhydrous sodium sulphateand evaporated under vacuum. A brownish solid was obtained whichcrystallised in water giving 1.4 g of (13) in the form of whitecrystals.

Yield=64%.

MS: m/z: 245-247-249 (80%-100%-25%: M+); 210-212 (80%-75%: M+—Cl); 131(100%: M+-Cl—Br), 105 (50%).

¹H-NMR (200 MHz, CDCl₃): δ 3.84 (s, 3H, N—CH₃); 7.25 (d, J=6.11 Hz, 1H,═N—CH═CH—), 8.23 (d, J=6.11 Hz, 1H, ═N—CH═CH—).

4-chloro-1-methyl-2-(triazol-2-yl)-1(H)-imidazo[4,5-c]pyridine (14) and4-chloro-1-methyl-2-(triazol-1-yl)-1(H)-imidazo[4,5-c]pyridine (14a)

250 mg of NaH (80% in paraffin, 8.6 mmol) were suspended in 5 ml ofanhydrous DMF and 0.5 ml (8.6 mmol) of 1(H)-1,2,3-triazole added. Thiswas left under stirring at room temperature for one hour, then thetemperature adjusted to 100° C. To this hot solution was added dropwise,over the course of 30 minutes, 1.4 g (5.7 mmol) of (13) emulsified in 15ml of hot, anhydrous DMF. This was left under stirring at 100° C. for 4hours, and then the temperature reduced to 60° C., and left to reactovernight.

Upon termination of the reaction the DMF was evaporated and the solidresidue crystallised in water.

The crystals were collected by filtration and the mother liquorextracted with methylene chloride, the organic phases combined and driedover sodium sulphate, evaporated and re-crystallised again in water. 614mg of a mixture of (14 and 14a) were obtained, in the form of whitecrystals.

Total yield=46% (14+14a). (14):

MS (m/z): 234-236 (100%-30%: M+); 207-209 (20%-5%: M+—HCN); 153-155(40%-10%).

¹H-NMR (CDCl₃, 200 MHz): δ 4.13 (s, 3H, N—CH₃); 7.35 (d, J=5.62 Hz, 1H,═N—CH═CH—), 8.05 (s, 2H, Triazole), 8.33 (d, J=5.62 Hz, 1H, ═N—CH═CH—).

(14a):

MS (m/z): 234-236 (10%-3%: M+); 206-208 (100%-35%: M+—N₂); 191-193(40%-15%).

¹H-NMR (CDCl₃, 200 MHz): δ 4.23 (s, 3H, N—CH₃); 7.39 (d, J=5.80 Hz, 1H,═N—CH═CH—), 7.93 (d, J=1.19 Hz, 1H, Triazole), 8.34 (d, J=5.80 Hz, 1H,═N—CH═CH—), 8.65 (d, J=1.19 Hz, 1H, Triazole).

4-benzylamino-1-methyl-2-(triazol-2-yl)-1(H)-imidazo[4,5-c]pyridine (15)

In a flat-bottomed, long-necked reaction flask was suspended 1.4 g (5.5mmol) of mixture (14,14a), in 5 ml of benzylamine. The reaction wasplaced inside a microwave oven (frequency of irradiation: 2,450 MHz) andirradiated at 460 Watts until the benzylamine boiled. This was boiledfor a few seconds and then the irradiation stopped and the mixtureallowed to cool. This operation was repeated until the starting productshad disappeared, as monitored by TLC. Following cooling, a yellow waxymass was obtained which was further purified by flash chromatography(gradient: cyclohexane/ethyl acetate 4:6 (100 ml), cyclohexane/ethylacetate 2:8 (100 ml), ethyl acetate). 390 mg of (15) was obtained as ayellow solid.

Yield=29%.

M.p.=180-184° C.

MS (m/z): 305 (BP, M+); 250; 200, 174, 148.

¹H-NMR (CDCl₃, 200 MHz): δ 4.02 (s, 3H, N—CH₃); 5.87 (bs,2H), 7.29 (d,J=6.90 Hz, 1H), 7.40-7.50 (m, 5H) 7.88 (d, J=6.90 Hz, 1H), 8.29 (s, 2H,Triazole).

4-amino-1-methyl-2-(triazol-2-yl)-1(H)-imidazo[4,5-c]pyridino triflate(16) (ST 1680)

183 mg of (15) (0.6 mmol) were dissolved in 5 ml of anhydrous methylenechloride and 0.7 ml of trifluoromethanesulphonic acid (6 mmol) addedslowly, dropwise. This was left to reflux for 1.5 hours. The reactionmixture was then chromatographed on an alumina column, eluted first withmethylene chloride (100 ml), then with methylene chloride/ethanol 50/50(100 ml) and finally with pure ethanol. The desired products wererecovered in the alcoholic moieties. Following evaporation of thesolvent, the residue was triturated using ethyl ether and thencrystallised in ethanol. 52 mg of pure ST 1680, were obtained.

Yield=24%.

M.p.: >290 (dec.)° C.

MS (of the free base): m/z: 215 (100%: M+); 160 (40%-5%); 134 (35%).

¹H-NMR (DMSO-d6, 200 MHz): δ 3.99 (s, 3H, N—CH₃); 7.37 (d, J=6.84 Hz,1H, ═NH+—CH═CH—), 7.82 (d, J=6.84 Hz, 1H, ═NH+—CH═CH—), 8.41 (s, 2H,Triazole), 8.62 (br, 1H, NH₂), 12.94 (s, 2H, ═NH+CH═CH—).

The compounds according to the present invention are ligands of theadenosine A_(2a) receptor, in particular, they are selectiveantagonists, and as such are useful as medicaments, in particular forthe treatment of pathologies benefiting from an antagonistic activitytowards the A_(2a) receptor.

Amongst the pathologies treated with the compounds of the presentinvention are motor disorders. As pathologies treated by the presentinvention we cite Alzheimer's disease, Huntington's disease, Wilson'sdisease and Parkinson's disease.

The present invention is also applied to Parkinson's disease associatedwith “on-off” phenomena, with preponderant dyskinesia.

In a preferred embodiment of the present invention, the compoundsdescribed are in combination with L-DOPA or with one or more dopamineagonists. In this case, the present invention is useful in dopaminesubstitutive therapy.

In another embodiment of the present invention, the compounds describedabove are useful as active ingredients for the preparation of amedicament for the treatment of cerebral ischaemia and-or the mechanismsassociated with neurodegenerative processes.

Molecular Pharmacology

Affinity Towards the Adenosine A_(2a) Receptor

The interactive capacity of each product towards the adenosine A_(2a)receptor was evaluated using membranes from HEK 293 cells (human embryokidney cells) stably expressing the human A_(2a) receptor subtypeexclusively.

The membranes were incubated with [3H]-CGS21680 at a concentration of 30nM in a buffer comprised of 50 mM Tris (pH 7.4); 120 mM NaCl; 10 mMMgCl₂ mM CaCl₂, 2 U/ml of adenosine deaminase for 90′ at 25° C.Non-specific binding was measured in the presence of NECA (50 μM).

Affinity Towards the Adenosine A_(2b) Receptor

The interactive capacity of each product towards the adenosine A_(2b)receptor was evaluated using membranes from HEK 293 cells stablyexpressing the human A_(2b) receptor subtype exclusively.

These membranes were incubated with [³H]-DPCPX at a concentration of 100nM in a buffer comprised of 50 mM Tris (pH 7.4); 120 mM NaCl; 5 mM KCl;10 mM MgCl₂; 2 mM CaCl₂, 2 U/ml of adenosine deaminase for 90′ at 25° C.Non-specific binding was measured in the presence of NECA (50 μM).

Affinity Towards the Adenosine A₁ Receptor

The interactive capacity of each product towards the adenosine A₁receptor was evaluated using membranes from CHO-K1 cells which stablyexpress the human A₁ subtype.

These membranes were incubated with [3H]-DPCPX at a concentration of1.66 nM in a buffer comprised of 50 mM Tris (pH 7.4); 120 mM NaCl; 5 mMKCl; 10 mM MgCl₂; 2 mM CaCl₂, 2 U/ml of adenosine deaminase for 90′ at25° C. Non-specific binding was determined in the presence of DPCPX(8-Cyclopentyl-1,3-dipropylxanthine) at a concentration of 1 μM.

Affinity Towards the Adenosine A₃ Receptor

For compounds ST 1535 and ST 2097 their affinities towards the adenosineA₃ receptor were determined.

For this study, membranes from HEK-293 cells, which stably express thehuman A₃ subtype, were used, according to the method described bySalvatore et al. Proc. Natl. Acad. Sci. USA, 1999 90:10365-10369. Theexperimental conditions required the use of [¹²⁵I]AB-MECA as aradioligand at a concentration of 0.1 nM, an incubation time of 90minutes at a temperature of 22° C., and IB-MECA (1 μM) for thedetermination of non-specific binding.

Analysis and Expression of the In Vitro Results

In binding studies for each compound, eight different concentrations(from 10⁻⁵ M to 10⁻¹² M) were evaluated in order to obtain competitioncurves. By means of non-linear regression analysis of the competitioncurves, the IC₅₀ values, which express the binding affinity of eachproduct, were determined. Using the Cheng Prusoff equation(K_(i)=IC₅₀/1+(L/K_(d))) K_(i) values were calculated through which theaffinity of each product studied, for the receptor investigated, isexpressed.

General Pharmacology

Evaluation of the Effects on Spontaneous Motor Activity in Mice

For this study, type CD1 male mice (n=8) were used. The effects of theproducts under study and of the reference compounds were evaluated usingan apparatus consisting of a Plexiglas cage (40 cm×40 cm) surrounded bya series of photocells which monitor the movements of the animals placedinside, connected a computerised system, through which, the signals arecollected and later elaborated.

Tests were carried out, after endoperitoneal administration of theproducts. 15 minutes after treatment, the treated animals, alternatingwith the controls, were placed inside the cage so as to record theirspontaneous movements over a total period of 45 minutes broken down intotwo observation intervals (15′-45′ and 45′-60′, with respect to the timeafter treatment).

To examine the possible effects of the compounds studied on motoractivity, the following parameters were considered: horizontal activity,vertical activity: total distance.

Except for CGS 21680 (reference compound, described in EP 0 277 917,Ciba-Geigy) which was dissolved in 0.9% NaCl, the products studied weresolubilised in DMSO and then diluted in Cremofor EL and 0.9% NaCl (finalconcentrations: DMSO 15%, Cremofor EL 15%, NaCl 0.9%.

Evaluation of the Capacity of the Products to Induce Catalepsy in Mice.

10 CD1 male mice were used per group. For this test, a steel bar, 10 cmlong, was placed at a height of 4.5 cm above the support surface. Ontothis, were placed the front legs of the animals. The presence ofcatalepsy was determined by measuring the time (in seconds) the animalremained in the posture placed. Later, this parameter was placedrelatively, on a scale of rising values (0 to 5) through which, thedegree of catalepsy determined in both control animals and in thesesubjected to treatment with the substances under test could beproportionately expressed.

The reference products and these in this study were administeredendoperitoneally, in a volume of 10 ml/kg, 30 minutes prior to the test.

Except for CGS 21680 (reference compound) which was dissolved in 0.9%NaCl, the products in the study and the control antagonist ZM 241385were solubilised in DMSO and then diluted in Cremofor EL and 0.9% NaCl(final concentrations: DMSO 15%, Cremofor EL 15%, NaCl 0.9%).

Evaluation of the Capacity of the Products to Antagonise CGS 21680Induced Catalepsy

For this study, the product ST 1535 was used. Catalepsy was induced inthe animals through the intracerebroventricular administration of CGS21680 (10 μg/5 μl/mouse), 30 minutes prior to testing for the catalepsyscore. The test compound was administered orally at a dose of 5 mg/Kgand 10 mg/Kg , 30 minutes prior to treatment with CGS 21680.

The catalepsy score was derived in the manner described followingtreatment with OGS 21680 after the following times: 30′, 60′ 120′, 180′.

Evaluation of the Capacity of the Products to AntagoniseHaloperidol-induced Catalepsy

For this study, product ST 1535 was used. Catalepsy was induced in theanimals through the endoperitoneal administration of Haloperidol at adose of 4 mg/Kg, two hours prior measuring catalepsy in the animals, thepresence of which was determined according to the method describedpreviously.

After scoring for catalepsy by Haloperidol, the animals were treatedorally, with a dose equal to 10 mg/kg and 20 mg/kg of the product ST1535. Then 60 minutes after treatment, the animals were subjected tofurther catalepsy scoring, which was carried out at the following timesafter ST 1535 administration: 120′, 240′, 300′.

Effect of the Administration of Associated L-DOPA and A_(2a) Antagonistson Haloperidol-Induced Catalepsy.

For this study, product ST 1535 was used.

CD1 mice, divided into different experimental groups (n=10 per group)were used. All animals were subjected to treatment with Haloperidol (4mg/kg, i.p.) two hours and 30′ prior to the catalepsy test, carried outaccording to the method described above.

Later, the animals were subjected to different types of treatmentaccording to their original experimental group (see diagram). Allcatalepsy evaluations were carried out 2 hours and 30 minutes afterHaloperidol treatment.

Haloperidol+ST 1535: ST 1535 2.5 mg/kg, per os, 75′ prior to testing;

Haloperidol+benserazide+L-Dopa: Benserazide 3.12 mg/kg i.p., 90′ priorto testing;

L-DOPA:. 12.5 mg/kg, 60′ prior to testing;

Aloperidol+benserazide+L-Dopa+ST 1535: Benserazide 3.12 mg/kg i.p., 90′prior to testing;

ST 1535 1.25 mg/kg or 2.5 mg/kg, 75′ prior to testing;

L-DOPA 12.5 mg/kg, 60′ prior to testing;

A_(2a) Antagonists and Antidepressant Activity. Forced Swim Test in Mice

Mice were dropped individually into glass cylinders (height: 25 cm,internal diameter 10 cm) containing 10 cm water, maintained at 23° C.The immobility time (sec) was measured during 4 minutes of test. A mousewas judged to be immobile when it remained floating in the water, makingonly the necessary movements to keep its head above water. Test compoundST 1535 was administered orally to mice, 60 minutes before the test.

In Vitro Activity

Table 1 reports values of the mean and standard deviations of theaffinity towards the adenosine A_(2a) receptor, expressed as K_(i) (nM)for the various compounds studied.

It is possible to observe that the products denominated respectively ST1535, ST 1537 and ST 2097 exhibit elevated interactive capacity towardsthe adenosine A_(2a) receptor.

The comparison of the affinity values of these compounds, with theserelative to the other products with adeninic structures, denotes thatthe substitution of adenine in position two, with relatively long alkylchains (see ST 1535, ST 2097) or with significant steric hindrance (seeST 1537), favours an increase in affinity towards the A_(2a) receptor.

In the same table are reported affinity values towards the adenosinereceptor subtypes A_(2b) and A₁, of each compound studied and, the ratioof receptor affinity (K_(i)A₁,/K_(i)A_(2a)), through which is determinedthe selectivity of each product.

It is observed that compounds ST 1535, ST 1537 and ST 2097 possess aninteractive capacity for the A_(2a) receptor prevalent with respect tothat demonstrated towards the A₁ and A_(2b) subtypes, therefore, thecompounds according to the present invention possess selective affinitytowards the A_(2a) receptor.

Furthermore, for compounds ST 1535 and ST 2097 the affinity for theadenosine A₃ receptor and for 36 receptors belonging to otherneurotransmitters have been evaluated. In these binding studies,compounds of interest were initially tested at a concentration of 1 μM.Later, if the compound displaced more than 50% of the specificradioligand it was evaluated at 8 different product concentrations todetermine the IC₅₀ values.

The results relating to this binding study are reported in table 2.

Compounds ST 1535 and ST 2097 display relatively low and negligibleaffinity towards the adenosine A₃ subtype and have no interactivecapacity towards the other receptors (IC₅₀>1000 nM).

These results demonstrate that the compounds in the present inventionare selective, having selective affinity for the adenosine A_(2a)receptor.

TABLE 1 A_(2a) A_(2b) A₁ Compound K_(i) (nM) ± sd K_(i) (nM) ± sd K_(i)(nM) ± sd K_(i)A₁/K_(i)A_(2a) ST 1680 97 ± 23 926 ± 55  1563 ± 252  16ST 1491 70 ± 15  10 ± 1.4 0.15 ST 1535 2.29 ± 0.58 627 ± 45  107 ± 40 47 ST 2097  0.12 ± 0.033 153 ± 13  26.2 ± 6.55 217 ST 1537 2.34 ± 0.692330 ± 588  80 ± 13 34 ST 1490 46 0.43 0.009 CGS 21680 51 ± 13 ZM 2413850.11 ± 0.03 Alloxazine 3.8 ± 2.1 DPCPX  6.5 ± 0.95

TABLE 2 ST 1535 ST 2097 Reference compounds Receptors 1 μM Ki (nM) 1 μMKi (nM) IC₅₀ (nM) Ki (nM) A₃ (h) 1580 519 IB-MECA 1.2 0.84ADO_(transporter) 24 34 NBTI 0.30 α₁(non-selective) — — prazosin 0.86α₂(non-selective) — — yohimbine 95 β₁ — — atenolol 1,770 β₂ — — ICI118551 2.3 BZD — — diazepam 12 (central) D1 — — SCH 23390 0.66 D2 — —(+)butaclamol 8.9 D3 — — (+)butaclamol 5.1 D4.4 (h) — — clozapine 156 D5(h) — — SCH 23390 0.61 GABAa — — muscimol 16 GABAb — — baclofen 50GABA_(transporter) — — Nipecotic acid 10,100 AMPA — — L-glutamate 613Kainate — — Kainic acid 77 PCP — — MK-801 2.0 P2X — — α,β-MeATP 14 P2Y —— dATPα S 22 NMDA — — CGS 19755 967 H₁ — — pyrilamine 1.3 (central) M₁ —— pirenzepina 22 M₂ — — methoctramine 34 M₃ — — 4-DAMP 3.5 M₄ — — 4-DAMP1.9 M₅ — — 4-DAMP 2.0 Choline_(transporter) — — Hemicholinium-3 12Opiate — — naloxone 1.6 (non-selective) 5-HT_(1A) — — 8-OH-DPAT 0.665-HT_(2A) — — ketanserin 2.7 5-HT_(2C) (h) — — mesulergine 1.9 5-HT₃ (h)— — MDL 72222 9.3 5-HT₄ — — 5-HT_(5A) (h) — — serotonin 79 5-HT₆ (h) — —serotonin 421 NE transporter — — protriptyline 1.1 DA transporter — —GBR 12909 5.0 5-HT transporter — 13 imipramine 4.4 For the testcompounds, the results are expressed as a percent inhibition of controlspecific binding (mean values; n = 2). The symbol — indicates aninhibition of less than 10%.In Vivo Activity

To define the activity profile (agonistic or antagonistic) possessed bythe compounds of interest, their effects on motor activity in mice wereexamined. These were compared to these brought about by the followingreference compounds CGS 21680 (selective agonist of the A_(2a) receptor,EP 0 277 917) and ZM 241385 (selective antagonist of the A_(2a)receptor). It is noted that the agonists induce a depression in motoractivity, whilst the antagonists have stimulatory effects (NikodijeviccO., et. al. J. Pharm. Exp. Ther 257, 286-94, 1991).

In table 3, the results of the effects induced by compounds of interestand reference, on three parameters describing spontaneous motor activityin mice are illustrated. The values of the mean and the standard errorof each parameter observed are reported.

TABLE 3 Horizontal activity Vertical activity Total distance Intervalsof observation from the treatment Treatment 15′-45 45′-60 15′-45 45′-60′15′-45′ 45′-60′ Controls 5992 ± 484  3148 ± 1004 356 ± 62 117 ± 40 1394± 148 469 ± 125 CGS 21680 1608 ± 328  471 ± 254  27 ± 11 10 ± 1  504 ±106 121 ± 73  (0.5 mg/kg) Vehicle 5890 ± 856 2259 ± 452 330 ± 96 119 ±34 1315 ± 290 412 ± 121 (10 ml/kg) ZM 241385 8706 ± 473 4148 ± 241 680 ±64 362 ± 78 2280 ± 242 1022 ± 130  (15 mg/kg) ZM 241385 7035 ± 709 3505± 375  613 ± 102 282 ± 37 1725 ± 186 783 ± 165 (30 mg/kg) ZM 241385 7790± 980 4241 ± 407  570 ± 129 264 ± 56 2250 ± 401 1131 ± 158  (60 mg/kg)ST 1537 7494 ± 565 3133 ± 250 590 ± 78 210 ± 17 1676 ± 204 677 ± 105(2.5 mg/kg) ST 1537 7203 ± 264 2844 ± 299 498 ± 77 363 ± 91 1503 ± 116532 ± 95  (5 mg/kg) ST 1537 8242 ± 847 3874 ± 295  528 ± 126 276 ± 572707 ± 950 843 ± 149 (10 mg/kg) Vehicle 5184 ± 832 1734 ± 367 123 ± 60 49 ± 25 (10 ml/kg) ST 1535 5386 ± 505 1693 ± 266 282 ± 79  68 ± 21 (2.5mg/kg) ST 1535 7549 ± 508 2353 ± 199 249 ± 41  76 ± 16 (5 mg/kg) ST 15357434 ± 526 2784 ± 345 219 ± 64  71 ± 32 (10 mg/kg) ST 1535 10524 ± 670 3321 ± 363 486 ± 84 148 ± 36 (20 mg/kg)

Regarding compounds in the present invention, in particular product ST1537 induces a clear increase in motor activity. In fact, independentlyof the product dosage administered, each of the parameters examined issignificantly increased with respect to control values. Furthermore, itis observed that compound ST 1537 is more active than the referenceantagonist. In fact, the minimum dose of ST 1537 induces the sameeffects as these produced, with a greater dose (15 mg/kg), of compoundZM 241385. Also for compound ST 1535 a significant increase of thespontaneous motor activity in mice is observed, starting from a dose of5 mg/Kg. Therefore, the compounds in the present invention possess anantagonistic activity towards the adenosine A_(2a) receptor.

Along with these observations, the evaluation of the eventual presenceof catalepsy in the animals, following treatment with the productsstudied (FIG. 1), confirms an antagonistic profile for ST 1537 and forST 1535. In fact, none of them brought about the appearance of catalepsyin mice, analogous to the reference antagonist (ZM 241385, 60 mg/kg) andin contrast to that demonstrated by the reference agonist (CGS 21680, 2mg/kg).

For compound ST 1535 the profile of antagonistic activity towards theA_(2a) receptor has been demonstrated also through the evaluation of itscapacity to antagonise the disappearance of catalepsy previously inducedby the administration of the selective A_(2a) receptor agonist: CGS21680(FIG. 2).

The selective A_(2a) receptor agonist induced an elevated degree ofcatalepsy in the animals. The product ST 1535, administered orally,significantly antagonises the appearance of catalepsy at all theobserved times, particularly when the dose administered is 10 mg/kg.This result confirms and describes the antagonistic activity profiletowards the adenosine A_(2a) receptor of preferred compound ST 1535.

The profile as selective, antagonist for the adenosine A_(2a) receptorof ST 1535 was confirmed also through the study of the effects of thecompound on Haloperidol catalepsy in mice. Furthermore, through thisevaluation the products capacity to modulate a dysfunction ofdopaminergic transmission in the nigrostriatal system was determined. InFIG. 3 it is observed that after oral administration, ST 1535 reducesthe appearance of catalepsy in mice, a behavioural manifestationpromoted by a reduction of the dopaminergic tone in the nigrostriatalsystem, following acute administration of Haloperidol. Theanticataleptic activity of ST 1535 demonstrates, indirectly, that thecompound of interest is capable of compensating the deficiency indopaminergic neurotransmission brought about in the nigrostriatal systemfollowing treatment with Haloperidol, according to the pharmacologicalcharacteristics belonging to selective antagonists of the adenosineA_(2a) receptor.

Furthermore, for the preferred compound ST 1535 it has been demonstratedthat the oral administration of the product potentiates theanticataleptic activity of treatment with ineffective doses of L-DOPAand benserazide. The results of this evaluation are reported in FIG. 4.Treatment with ST 1535 associated with ineffective doses of L-DOPA andbenserazide reduce

Haloperidol-catalepsy, in a Dose-dependent Manner.

These results suggest that the product of interest ST 1535 can beadministered in combination with low doses of L-DOPA for the treatmentof Parkinson's disease.

L-DOPA is commonly used for the treatment of Parkinson's disease. Yet,the use of L-DOPA becomes limited due to the appearance of dyskinesia asa side effect (Shaw K. M. et al. “Q. J. Med” 1980 49, 283). Theco-administration of ST 1535 could reduce the quantity of L-DOPA to beadministered, reducing the appearance of said side effects.

Furthermore, for the preferred compound ST 1535 an antidepressantactivity was measured. It is noted that selective antagonists of theA_(2a) receptor are being defined as new potential antidepressants (ElYacobui M. et al. British J. Pharmacol. 2001:134, 68-77). FIG. 5represents the effects of ST 1535 in an animal model for depression. Thecompound reduces, in a dose-dependant manner, the time of immobility ofthe animal, in a manner similar to that observed for the antidepressivedrug Imipramine.

A further object of the present invention are pharmaceuticalcompositions comprising, as active ingredient, at least one formula (I)compound, alone or in combination with one or more other formula (I)compounds, or, said formula (I) compound or compounds in combinationwith other active ingredients useful in the treatment of the pathologiesindicated here, for example other products with activity towards theadenosine A_(2a) receptor; even in separate dosage forms or in formsadapted to combined therapies. The active ingredients in the presentinvention will be in mixtures with appropriate vehicles and/orexcipients commonly used in pharmaceutical techniques, as for example,described in “Remington's Pharmaceutical Sciences Handbook”, latestedition. The compositions according to the present invention willcontain a therapeutically effiective amount of the active ingredient.The dosages will be determined by a person skilled in the art, forexample clinicians and doctors, according to the type of pathology to betreated and the conditions of the patients, or in concurrence with theadministration of other active ingredients.

Examples of pharmaceutical compositions are those that permit oral orparenteral, intravenous, intramuscular, subcutaneous, transdermaladministration. Pharmaceutical compositions suitable to this purposeare: pills, rigid or soft capsules, powders, solutions, suspensions,syrups, solid forms for extemporary liquid composition. Compositions forparenteral administration are for example all the forms injectableintramuscularly, endovenously, subcutaneously, in the form of solutions,suspensions, emulsions. We also mention liposomal formulations. Alsoincluded are the controlled-release forms of the active ingredient, bothfor oral administration, pills covered with appropriate layers,microencapsulated powders, complexes with cyclodextrine, depot forms,for example subcutaneous, such as injectable deposits or implants.

1. A compound of the formula

wherein: X is CH; R₁ is C₁-C₆ linear or branched saturated orunsaturated alkyl; R2 is hydrogen or C1-C6 alkyl R₃ is NH₂, NHR₄ R₄ isC₁-C₆ alkyl or C₁-C₆ hydroxyalkyl, C₁-C₃ alkoxyalkyl, amino(C₁-C₆)alkyl,where the amino group is optionally substituted with one or two C₁-C₃alkyl groups, being said alkyl groups linear or branched saturated orunsaturated, C₆-C₁₄ aryl or C₆-C₁₄ aryl(C₁-C₆)alkyl, with the aryl groupoptionally substituted by one or more substituents, either the same ordifferent, selected from the group consisting by halogen, hydroxy, C₁-C₆alkoxy linear or branched saturated or unsaturated, amino, mono- ordi-substituted with C₁-C₆ alkyl linear or branched saturated orunsaturated; and pharmaceutically acceptable salts thereof.
 2. Thecompound according to claim 1, wherein X is CH and R₂ is hydrogen.
 3. Aprocess for the preparation of a compound according to claim 1,comprising, according to the following diagram, the following steps:

a) bromo-substitution at position 2 of compound a), b) substitutingbromo at position 2 of compound b) with a triazol-2-yl group to givecompound c).
 4. A pharmaceutical composition comprising at least onecompound of claim 1 mixed with pharmaceutically acceptable excipientsand/or vehicles.